Create a 1 microsecond timer in nRF52832

[chianglin]

Hi,

As well know, there have a nrf_delay_us() function can execute very short delay time, but the function can only "delay".

If I want to create a 1 microsecond continuous timer, and it can change some GPIO pin status when timer-IRQ ioccur.

How to create this kind of timer?

Would you please give me an example code?

Thank you,

Ives

[Sigurd]

Hi

If I want to create a 1 microsecond continuous timer, and it can change some GPIO pin status when timer-IRQ ioccur.

Do you want to create some PWM signal or something? Then I suggest using the PWM peripheral instead.

[chianglin]

HI,

Actually, I want to simulate a 1MHz I2C server, but nrf52832's I2C master can only support 400KHz.

Thank you

[Sigurd]

Hi!

chianglin said:

I want to simulate a 1MHz I2C server

For a 1MHz signal, I suggest using TIMER+GPIOTE+PPI.

See the code in this post: 

 RE: nRF52 clock in and out 

adjust the  " NRF_TIMER1->CC[0] = 1; // Adjust the output frequency by adjusting the CC." , to get the desired frequency 

chianglin said:

nrf52832's I2C master can only support 400KHz.

For nRF5340 we have 

• Supported baud rates: 100, 250, 400 and 1000 kbps -> https://infocenter.nordicsemi.com/topic/ps_nrf5340/twim.html?cp=4_0_0_6_35

[chianglin]

Hi,

Thank you for your example code.

It looks this example code can only toggle GPIO-pin?

When using continus timer, it will trigger a IRQ-handler while time-out, and I can do somethings (ex. Implement the I2C protocol)

Does "TIMER+GPIOTE+PPI" can trigger an IRQ handler?

Thank you,

[Sigurd]

Hi!

You can take a look at this sample for that: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/nrf_dev_timer_example.html

PS: I'm not sure how well a bit-banged i2c at 1000 kbps on nrf52832 will work, if you are using BLE at the same time, it will likely affect the timing of the i2c.

[chianglin]

Hi,

I already test the method of timer, and it's maximum execute speed is 10us.

Its too slow for me.

Would you please tell me how to speed-up timer execute time? 

[chianglin]

Hi,

Wiould you please tell me about the minimum interrupt time of nRF52832 timer?

[Sigurd]

There is a delay(interrupt latency) when both entering and exiting the ARM Cortex -M4 ISR, + the SoftDevice also adds delay ~4us when enabled, ~2 when disabled, so overall, you won't be able to change the GPIO fast enough when doing it from interrupts.

https://infocenter.nordicsemi.com/topic/sds_s132/SDS/s1xx/processor_avail_interrupt_latency/interrupt_latency_soc_framework.html